1. Field of the Invention
The present invention relates a control system of an engine and also relates to a control method of the engine.
2. Description of the Related Art
An engine generally has an intake device, which is provided with a solenoid valve to control an amount of intake air on the basis of a xe2x80x98DUTY CONTROLxe2x80x99 (herein, merely called xe2x80x9cduty controlxe2x80x9d), in order to make idling of the engine stable and improve starting performance.
It is necessary to perform an initial setting of an amount of intake air periodically to increase the above-mentioned performance to at least a certain level. Such an initial setting (initializing) operation generally requires a duty tester and the other exclusive tools.
However, all the dealers and maintenance facilities do not necessarily always have the duty tester and the other exclusive tools. In addition, any user will also not have them individually. As a result, there is a restriction in the initial setting operation and too much expenses are required. Moreover, the initializing operation is also required when shipping the engine from a manufacturing plant, and the use of the duty tester and the other exclusive tools will deteriorate the workability.
In view of such circumstances, there may be adopted measures to make an indirect duty adjustment, without using any exclusive tools, by for example closing an intake port of the solenoid valve with a finger and turning, in such a state, an air bypass screw to adjust a bypass flow rate so as to adjust the revolution number to a level, which is lower than the target revolution number. In such a case, a careful adjusting operation is required, it is not easy to carry out such an adjusting operation and the adjusting operation does not necessarily provide good results.
Further, when the amount of air is adjusted to a side relying on the solenoid, i.e., a side of a high-solenoid duty, there occurs an inconvenience such as of deteriorated starting performance, stall at a time of conducting a sudden completely closing operation, increase in power consumption, and so on.
On the other hand, when the amount of air is adjusted to an opposite side to the side relying on the solenoid, i.e., a side of a low-solenoid duty, an excessive amount of air may deteriorate reduction in revolution number of the engine during deceleration, causing difficulty in a shifting operation or increase the revolution number in an idling state, deteriorating the rate of fuel consumption. With respect to an engine of an outboard motor, for example, the engine operates in the idling state to carry out a trolling. Increase in the revolution number in the idling state makes the speed of a boat faster, thus deteriorating maneuvering properties of the boat.
In either case mentioned above, an inappropriate adjustment will not provide a full performance of the engine.
Furthermore, as mentioned hereinbefore, the intake device of the engine is provided with a solenoid valve to control an amount of intake air on the basis of a duty control so as to make idling of the engine stable and improve starting performance.
Such solenoid valve is controlled so that the revolution number of the engine becomes an aimed revolution number except for a case of full-close state of a throttle valve or starting and dashpot mode.
On the other hand, in the case of not full-close state of the throttle valve, the duty is regulated on a predetermined map so as not to be delayed through a dashpot control at a time of rapid full-close operation.
Furthermore, the solenoid valve of the engine is also controlled, even in the full-close state, in a range not causing a problem in the stating characteristic, rotation-down, engine stall or like at the dashpot control time.
However, the adjustment or control mentioned above is not always performed and, in practical, is carried out only at a time of inspection of the engine or occurrence of an inconvenient matter. Accordingly, there causes a difference between the preliminarily adjusted air amount and an air amount actually required for the engine in accordance with aged deterioration, degradation of lubrication oil, friction change or like.
For example, in a case where a sensor utilized for the control is a full-close switch performing xe2x80x9cONxe2x80x9d operation at a full-close time of a throttle valve disposed inside a throttle body, a revolution number feed-back function is caused at the full-close time and no problem is, hence, caused. However, in xe2x80x9cOFFxe2x80x9d state of the full-close switch, i.e., in a case where the full-close switch is even little opened, the duty is controlled on the preliminarily determined map, so that there may cause a case that the revolution number of the engine is increased or decreased at the ON-OFF switching point of the full-close switch.
For example, in a case where the duty at the time of feed-back in the xe2x80x9cONxe2x80x9d state of the full-close switch is set to be higher than a duty in the xe2x80x9cOFFxe2x80x9d state thereof, the air amount is reduced at the switching point (ON OFF) and the engine revolution number is suddenly lowered.
Furthermore, in a case where the throttle valve is returned slowly, there is a possibility of causing a case that an air amount is reduced just before the xe2x80x9cONxe2x80x9d state of the full-close switch and the engine stall is caused.
On the other hand, in a case where the duty at the time of feed-back in the xe2x80x9cONxe2x80x9d state of the full-close switch is set to be lower than a duty in the xe2x80x9cOFFxe2x80x9d state thereof, the air amount is increased at the switching point (ON OFF) and there may cause an inconvenience such that the engine revolution number is suddenly increased.
Even in a case where a throttle sensor for detecting a degree of throttle valve opening is utilized in place of the full-close switch operating at the open/close time of the throttle valve for the dashpot control or like, an inconvenient state substantially identical to that mentioned above will be caused at the switching point thereof because the throttle sensor is provided with an idle zone.
A primary object of the present invention is to substantially eliminate defects or drawbacks encountered in the prior art mentioned above and to provide control system and method of an engine, which permits to initialize easily an amount of intake air without using any exclusive tools in a reliable manner.
Another object of the present invention is to provide, in addition to the above, control system and method of an engine capable of preventing a change of revolution number of the engine at a switching (open/close) point of a throttle valve of the engine.
These and other objects can be achieved according to the present invention by providing, in one aspect, a control system of an engine, in which an intake device is provided with a solenoid valve and an amount of intake air is controlled on a basis of a duty control by an element of a control unit, wherein the control unit includes means for recognizing a state which is evidently different from a normal state to thereby stationarily hold a duty of the solenoid valve at a necessary set value.
According to this aspect, it is possible to easily initialize an amount of intake air with the use of a simple tool without considering the target amount of intake air and to prevent an engine stall from occurring during the adjustment operation.
In preferred embodiments of this aspect, the evidently different state from the normal state is caused by carrying out an operation for increasing a revolution number of the engine in a fully closed state of a throttle valve. A time elapsed is set for increase in the revolution number of the engine.
The evidently different state from the normal state is caused by carrying out an operation for setting a voltage level of a terminal in a harness to a level, which is different from a normal voltage level.
The evidently different state from the normal state is caused by carrying out a switching operation of a specific switch.
The duty is set to be held stationarily after the recognition of a warming up state of the engine. The duty may be set to be held stationarily after recognition that a shift device takes a neutral state in a shift position thereof.
An information that the duty is stationarily held is transmitted to an operator by at least either one of a display device and an audio response device.
An adjustment of the duty is automatically stopped after the engine is stably and continuously operated for a set period of time within a range of an error of a target revolution number.
An information on completion of an operation for stationarily holding the duty is transmitted to an operator by at least either one of a display device and an audio response device.
The engine is set to be stopped immediately after the operation for stationarily holding the duty is failed.
According to preferred embodiments, it is possible to prevent an amount of air from being erroneously held stationarily. It is also possible to make a set range of amount of air narrow, reducing the adjustment variation to the minimum. The safety during working can be ensured.
No exclusive tool is required to carry out an adjusting operation, thus further ensuring an easy working. Furthermore, it is possible to make easily adjustment and prevent the subjectivity of an operator from being incorporated into the working and to ensure safety of the operator.
In another aspect, there is provided a control method of an engine having an intake device provided with a solenoid valve and a control unit, wherein an amount of intake air is controlled on a basis of a duty control by the control unit, and a duty of the solenoid valve is stationarily held to a necessary set value through recognition, to the control unit, of a state which is evidently different from a normal state to thereby stationarily hold a duty at a necessary set value.
In a further aspect, there is also provided a control system of an engine having an intake device provided with a throttle body and a solenoid valve to control an amount of intake air on a basis of a duty control, wherein a full-close switch is kept in an xe2x80x9cONxe2x80x9d position when a throttle valve mounted to the throttle body is fully closed, and a duty for the solenoid valve is set, when the full-close switch is switched from the xe2x80x9cONxe2x80x9d position to an xe2x80x9cOFFxe2x80x9d position, to stationarily hold the duty as it is without causing variation in an adjusted value for the solenoid valve at a time when a switching operation of the full-close switch is carried out.
According to this aspect, at a time of switching the full-close switch from the ON position to the OFF position, the rapid change of the engine revolution number can be prevented at time of a minute or fine open/close control of the throttle valve of the engine.
In preferred embodiments of this aspect, a map gradient is offset so as to leave the gradient as it is and pass through a duty value as held. The adjusted value at a time when the full-close switch is switched from the xe2x80x9cONxe2x80x9d position to an xe2x80x9cOFFxe2x80x9d position is reflected in the map in a case where the full-close switch is kept in the xe2x80x9cOFFxe2x80x9d position. The offsetting is conducted by determining a revolution number of the engine and the adjusted value at a time when the full-close switch is switched from the xe2x80x9cONxe2x80x9d position to an xe2x80x9cOFFxe2x80x9d position, in accordance with differences from similar lattice points in a basic map. Upper and lower limits are provided for an amount of the offsetting.
According to these preferred embodiments, the map is moved itself in accordance with the air amount, and the engine revolution is performed in a normal change or variation in increasing or decreasing mode, thus ensuring a normal and steady operation.
Furthermore, the behavior of the engine revolution number due to the open/close operation of the throttle valve after the switching to the xe2x80x9cOFFxe2x80x9d position of the full-close switch valve can be made substantially equal to that in the normal operation.
Still furthermore, the adjusted value at a time when the full-close switch is switched from the xe2x80x9cONxe2x80x9d position to the xe2x80x9cOFFxe2x80x9d position in accordance with differences from similar lattice points in a basic map, so that the possibility of occurrence of engine stall will be effectively eliminated.
In addition, even if the switching from the xe2x80x9cONxe2x80x9d position to the xe2x80x9cOFFxe2x80x9d position of the full-close switch be made at a time of just after the engine starting or during the dashpot operation, the possibility of occurrence of rapid lowering of the engine revolution or lowering thereof will be effectively eliminated.
In a still further aspect, there is also provided a control method of an engine having an intake device provided with a throttle body and a solenoid valve to control an amount of intake air on a basis of a duty control, wherein a full-close switch is kept in an xe2x80x9cONxe2x80x9d position when a throttle valve mounted to the throttle body is fully closed, and a duty for the solenoid valve is set, when the full-close switch is switched from the xe2x80x9cONxe2x80x9d position to an xe2x80x9cOFFxe2x80x9d position, to stationarily hold the duty as it is without causing variation in an adjusted value for the solenoid valve at a time when a switching operation of the full-close switch is carried out.
In the above aspects, the engine may preferably be an engine for an outboard in which a crankshaft is placed so as to extend vertically in an installed state.
The nature and further characteristic features of the present invention will be made more clear from the following descriptions made with reference to the accompanying drawings.